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F. Aumayr, E. Wolfrum, J. Schweinzer, D. Bridi, K. Igenbergs, J. Kamleitner:
"A sodium (Na) beam edge diagnostic";
Poster: 18th Intern. Conf. on Plasma-Surface-Interaction (18th PSI), Toledo/Spain; 27.05.2008; in: "Book of Abstract, 18th Intern. Conf. on Plasma-Surface-Interaction (18th PSI)", (2008), S. 243.

At ASDEX Upgrade a fast lithium (Li) beam diagnostic is installed which measures successfully edge electron densities, edge ion temperatures and impurity ion densities /1,2,3/. The replacement of Li by sodium (Na) promises some advantages: i) the emitter temperature can be kept lower, thus improving the withstand voltage and the stability of the ion source at higher voltages (>60 kV), ii) the charge exchange cross sections for collisions with relevant impurity ions (He, C) are larger, facilitating ion temperature measurements, iii) the lifetime of the observed transition (Na I (3p-3s)) is shorter than the Li I (2p-2s), which improves the signal/noise ratio at relevant radii and is of benefit not only to the temporal resolution of electron density measurements but also to the planned density fluctuation measurements /4/.
Recently, a complete data set of all relevant plasma particles (electron, proton) - Na collisions has been compiled /5/ and first experiments with a Na beam installed at ASDEX Upgrade have been carried out. A collisional radiative model is employed to calculate the beam attenuation in a plasma discharge as well as the occupation number of Na excited states (Na states included: n=3, 4 & 5s) using the above mentioned data set. Excellent agreement between modeled and measured emission profiles are found, proving the validity of the compiled data set. Moreover, it is shown, that the beam penetration of Na as compared with Li is not much deteriorated despite the lower velocity at the same acceleration voltage, which is mainly due to the fact that the higher excited states of Na are considerably less occupied than in the case of Li and consequently the very efficient charge exchange from these states plays a minor role only.

/1/ R. Brandenburg et al.. Fusion Techn. 36 (1999) 289-295
/2/ M. Reich et al., Plasma Phys. Control. Fusion 46 (2004) 797
/3/ E.Wolfrum et al., Rev. Sci. Instr. 77 (2006) 033507
/4/ S. Zoletnik et al., Phys. Plasmas 6 (1999) 4239
/5/ K. Igenbergs et al., At. Data Nucl. Data Tables in print.